The present invention relates to a method of installing ceramic fiber modules to a steel furnace shell for insulating the interior of a high temperature furnace.
For many years heat treating furnaces, ceramic kilns, brick kilns, and the like, were lined with dense fireclay brick. Later insulating firebrick replaced the dense fireclay brick because of its lighter weight and better insulating properties. Recently ceramic fiber material made of alumina-silica fibers made into blankets has replaced the insulating firebrick as lining for such furnaces and kilns. The latest advance in this art is the use of ceramic fiber modules in which the ceramic fiber blanket is cut to size and assembled into a module unit of varying sizes, but usually 12".times.12".times.desired thickness, with the blanket pieces or strips positioned edge grain, single fold or accordian folded and held together by various means to form a unit of construction that can be attached to a furnace wall by welding, screws, cement or other means.
The rolls of ceramic fibers typically are impaled upon alloy studs welded to the furnace walls. This arrangement has several drawbacks, namely that the temperature limit of the construction is dependent on the temperature that the alloy studs can stand. Another drawback is that the ceramic fiber blankets are easily damaged, torn and also tend to shrink with high temperature use so that gaps are formed between the edges of the blankets or shrinkage tears occur.
Recognizing the advantages of module construction over multiple layer construction, a number of module designs and retention devices have been developed.
Typical of such construction are the Sauder U.S. Pat. Nos. 3,819,468 and 3,993,237. These devices still require a welded stud on the furnace frame and time consuming application. Other patents exemplifying this type construction including Balaz et al U.S. Pat. No. 3,832,815 in which a series or strips or ceramic fibers are clamped together into a module for installation on furnace walls. Still other such devices are shown in Byrd U.S. Pat. Nos. 4,001,996 and 4,123,886.
Another patent showing a modular installation is Dunlap U.S. Pat. No. 4,248,023 which shows a shell filled with layered ceramic fiber blankets placed parallel to the furnace wall. Brady U.S. Pat. No. 3,854,262 shows a stack bonded construction using strips of ceramic fiber blanket and does not relate to modular construction.
In ceramic fiber module construction it is desirable to be able to utilize a single installation technique in many different types of installations. For example, in some constructions, it is desirable to apply a layer or layers of ceramic fiber blanket next to the steel shell to serve as a thermal barrier between the modules and the steel shell thereby overcoming any objections to possible heat leaks between modules and also reducing the cost of the lining, because less expensive blanket is used to make up part of lining thickness.
It also is necessary at times to apply a protective membrane or coating directly to the steel shell and to the retention bracket to protect from corrosion, etc.
It further is desirable in certain installations to apply a layer of either aluminum or stainless steel foil over the blanket and behind the modules to serve as a vapor barrier and at a distance from the steel shell to insure that the temperature is high enough to keep vapours above the dew point.
The present invention allows for all of the foregoing variations in installation and construction techniques and in addition, the brackets are welded in predetermined position on the steel shell so that the spacing between brackets is fixed and predetermined, thereby eliminating any possibility of worker error in determining the module density, which is critical to the design of the furnace.
The brackets and the pointed pins which engage the brackets and retain the modules to the wall are positioned within the body of the module away from the free surface of the module to protect the bracket and pins from the heat of the furnace.
Another advantage of the present construction comes about because the brackets are located a predetermined distance apart. As mentioned, this insures uniform and consistent module density and modules also may be installed from both ends of a wall or roof area by two crews with the assurance that when they come together, the closing modules in any given row will fit. This feature improves installation productivity. The closing modules are retained with extra long pins, inserted and then worked back into the closing module with needle-nose pliers which can be worked between the module folds without damage to the module.
Thus, it is a principal object of the present invention to provide a method and apparatus for fastening ceramic fiber modules to furnace walls in a variety of construction configurations using the same hardware. In particular, it is an object of this invention to provide a method of installing ceramic fiber modules in which retaining brackets are welded in a predetermined pattern to the steel shell of a furnace and the shell and bracket optionally can be coated with a corrosion resistant coating, a blanket of insulating fibers can be positioned adjacent to the furnace wall if desired, and a vapor barrier can be placed over the blanket before the modules of ceramic fibers are impaled on a slidable pin engaged with the end of the bracket.
It is a further object of this invention to provide a ceramic fiber module installation method in which the brackets are pre-located to predetermine the module density and the wall or roof can be installed from both ends simultaneously.
These and other objects and advantages will become apparent hereinafter.
The present invention comprises a method of applying ceramic fiber modules to the steel shell of a furnace in an efficient and workmanlike fashion eliminating potential worker errors and providing for the application of a variety of installations with a single system.